Between 25 and 35% of the adults in the US who could benefit from hearing aids, as many as 25,000,000 persons, either refuse to consider those devices or reject them after a trial. Many of those who try to use hearing aids decide that they are not able to understand speech well enough with them to justify their cost. While developments in hearing-aid technology have improved this situation, recent research suggests another answer. It is that speech perception training may improve recognition abilities to the point that otherwise unsuccessful hearing-aid users can become successful. Several research groups, including our own, have reported statistically significant improvements in speech recognition as a result of various types of training. But none have answered three vital questions. (1) How great an improvement in speech recognition can be achieved through prolonged systematic training? (2) How many hours of training are required to approach that limit? (3) What are the optimal training materials for successful speech recognition training: spoken phrases and sentences, the constituent parts of speech, or both speech parts and wholes? The proposed project, conducted at six major centers for auditory research and clinical service, will address these questions through an intensive speech perception training study of hearing-aid users. Training will be done using the Speech Perception Assessment and Training System (SPATS), which has been developed and tested over the past eight years. SPATS combines the training of over 100 of the most common syllable constituents of spoken English (onsets, nuclei and codas) with training on the recognition of meaningful sentences. Clinical trials with both hearing-aid and cochlear-implant users have shown improved post-training scores on speech recognition tests, following 12 to 24 hours of SPATS training, similar to results reported for other systems. Those data, together with evidence from non-speech auditory training research, suggest that clinically important gains would be made if the training continued for a total of 30-40 hours. While this amount of training may be considered an impossible demand to make of hearing-impaired persons, it is less forbidding when compared to the time devoted to learning many other skills. In 30- 40 hours a piano student can play a few scales and may have mastered her first elementary piece using two hands, an amputee who will eventually become a skier has managed to walk across a room, and a foreign-language student has learned to read a very simple story, slowly. Speech perception training for hearing-aid users should not be rejected out of hand because 30-40 hours of training does not fit the model of current clinical practice. If major improvements in speech reception by the hearing-aid user can be shown to be achievable through such training, many users would elect to make that effort and be willing to pay for it.